JP2000118146A - Heat sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the printed image preserving property of a recording part and the heat resistant base color stability of a white paper part by a method wherein a urethane compound, obtained by reacting a diphenol compound with a di-isocyanate compound under a specified molar ratio, is employed. SOLUTION: An excessive di-phenol compound is resolved in a solvent, such as acetone, methyl ethyl ketone, pyridine or the like, then, a di-isocyanate compound is added to the solution so that a molar ratio to the di-phenol compound becomes 1.01-10.0 to 1.0 or preferably 1.01-5.0 to 1.0 and the mixture is mixed for several hours at a room temperature. Thereafter, the solvent of reacted solution is removed and obtained solid body is dried to obtain the urethane compound. The compound is improved in color developing characteristics or printed image preserving property and the heat resistant base color stability of white paper part, however, these phenomena are considered due to that a urethane structure is provided in molecules and the amount of phenolic portion in the compound is comparatively small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermosensitive recording medium using a urethane compound as a color developer.

[0002]

2. Description of the Related Art In general, a thermosensitive recording medium is prepared by grinding and dispersing a colorless or pale-colored dye precursor, which is usually an electron-donating compound, and a developer, which is an electron-accepting compound, into fine particles. A coating solution obtained by mixing both, adding a binder, a filler, a sensitizer, a lubricant and other stabilizers to a support such as paper, synthetic paper, film, plastic, etc. A color record is obtained by an instantaneous chemical reaction caused by heating of a stamp, a laser beam or the like. These thermosensitive recording materials include measurement recorders, computer terminal printers, facsimile machines, automatic ticket vending machines,
It is applied to a wide range of fields such as barcode labels.

However, with the recent diversification of recording devices for thermosensitive recording media and the development of higher performance, the quality required for thermosensitive recording media has become higher. In addition, with the spread of plain paper recording methods such as the electrophotographic method and the ink jet method, the thermal recording method has more opportunities to be compared with these plain paper recording methods. For this reason, for example, it is required that the stability of the recording portion (image) of the thermal recording medium or the stability of the non-recording portion (ground color portion) before and after recording approaches the same level as that of the plain paper recording method. ing.
Especially from the point of storage stability of recorded images, light resistance, oil resistance,
There is a demand for a heat-sensitive recording medium having excellent water resistance and plasticizer resistance. Also, like the POS label system,
Even when used at a place where the environmental temperature is around 100 ° C., no background fog occurs (hereinafter, no background fog occurs even at a high temperature of 100 ° C. or higher is referred to as a heat-resistant ground color stability of a blank portion), and There is a demand for a thermosensitive recording medium having good image storability even in such an environment.

Heretofore, in order to improve the image storability and the like, epoxy compounds described in JP-A-4-97888, aziridine compounds described in JP-A-4-113888, and JP-A-63-22683 have been incorporated into a coloring layer. And the like containing various metal salts described in Japanese Unexamined Patent Publication (Kokai) No. H11-260, and the like. However, the effect is insufficient.

Therefore, in order to improve image preservability,
Instead of the conventionally used phenolic color developing agents, so-called non-phenolic color developing agents exhibiting an acidic atmosphere having no hydroxy group and capable of coloring the dye precursor have been developed. For example, urea and thiourea compounds described in JP-A-58-21496, and JP-A-4-28229.
Examples thereof include carbonyl sulfonamide compounds described in JP-A No. 1 and organic phosphoric acid compounds described in JP-A-6-99666. One of the causes of decolorization of the color image is the dissociation of the dye and the developer, but the non-phenolic developer is less soluble in water, oil, plasticizer, etc. than the conventional phenolic developer, It is considered that the image storability is improved. However, with some effect, the degree is still not enough. JP-A-5-147357 reports an example using a sulfonylurea compound as a color developer. Although good image storability is exhibited in oil resistance and plasticizer resistance, it tends to be slightly inferior in water resistance and cannot be said to have perfect performance.

On the other hand, among phenolic developers which are generally considered to have poor image storability, there are compounds having relatively good image storability. For example, JP-A-62-17
Sulfonamide compounds described in JP-A Nos. 0388 and 63-203380, and sulfone compounds described in JP-A-5-301446 and JP-A-8-198841. The phenolic developer is considered to exhibit good image storability since it is less soluble in water, oil, plasticizer and the like than a low-molecular phenolic developer such as bisphenol A. However, although they have some effect, their degree is still not enough.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material having improved image storability of a recording portion and heat-resistant ground color stability of a blank portion.

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the molar ratio of the diphenol compound to the diisocyanate compound is 1.01 to 1
The inventor has found that a urethane compound obtained by reacting at a ratio of 0.0 to 1.0 exerts an excellent function as a color developer of a thermosensitive recording medium, thereby completing the present invention. Particularly, a urethane compound synthesized using a diphenol compound represented by the following general formula (1) and a diisocyanate compound represented by the following general formula (2) is effectively used in the present invention.

[0009]

Embedded image (However, R ¹ and R ² each represent an alkyl group, an alkoxy group, or an electron-withdrawing group. L and m each represent an integer of 0 to 4. n and o each represent an integer of 1 to 5. A Represents a divalent group.)

Here, R ^{1 and} R ² may be any substituents which do not impair the color developability and image storability when the compound is used as a color developer. Among these, from the viewpoints of stability of color developing ability and color sensitivity, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom such as chlorine, bromine, fluorine, or a nitro group as an electron-withdrawing group. , An alkoxycarbonyl group and a nitrile group are preferred. In the compound represented by the general formula (2), A represents a divalent group. Representative examples of the group belonging to A are shown in the following formulas (6) and (7), but the present invention is not limited to these.

[0011]

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[0012]

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Further, urethane compounds obtained from diisocyanate compounds represented by the following formulas (3) to (5) are more useful.

[0014]

Embedded image

[0015]

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[0016]

Embedded image (P represents an integer of 2 to 12.)

The urethane compound used in the present invention is a mixture of a plurality of urethane compounds having different molecular weights obtained by reacting an excess diphenol compound with a diisocyanate compound. When synthesizing the urethane compound of the present invention, the molar ratio between the diphenol compound and the diisocyanate compound is 1.0.
The urethane compound mainly composed of high molecular weight becomes closer to the equimolar ratio of 1: 1.0, whereas the urethane compound of lower molecular weight becomes more mainstream when one of them is used in a large excess, such as 10.0: 1.0. Come. As shown in the following formula (8), one molecule of the diisocyanate compound reacts with two molecules of the diphenol compound to form a urethane compound, and then the remaining diisocyanate compound and the diphenol compound are added to the terminal phenol. This is because they react sequentially and this is repeated.

[0018]

Embedded image (However, A represents a divalent group, and r represents an integer of 3 or more.)

Actually, bis (4-hydroxyphenyl) sulfone <BPS>, which is a diphenol compound, and 1,6-hexamethylene diisocyanate <HDI>, which is a diisocyanate compound, are reacted at a molar ratio of 2: 1 to convert a urethane compound. The solubility in acetonitrile was measured, and the soluble matter as a low molecular weight component was 49%. As a result of HPLC analysis of the soluble matter, seven peaks were detected. From this, it is estimated that the generated urethane compound is a mixture of at least seven or more types.

In recent years, there has been an increasing demand for thermosensitive recording media not only for image storability but also for color development characteristics such as sufficient color development density even with low applied energy. The present inventors have found that a developer having good color-forming properties can be obtained by using a mixture of low-molecular-weight urethane compounds, and have successfully satisfied the demand. Although the reason for this is not clear, it is considered that the use of the urethane compound as a mixture has the effect of the eutectic point, in which the melting point is lower than that of the individual components. In other words, even with low applied energy, it can be melted and brought into contact with the dye to form a color. In addition, at the time of synthesis, by increasing the molar ratio of the diphenol compound instead of the diisocyanate compound, the possibility that a phenol structure is arranged at the terminal of the generated urethane compound increases,
It is presumed that the effect of improving the coloring characteristics is exhibited more.

Further, according to the present invention, not only the color development characteristics and the image storability are improved, but also the excellent heat-resistant ground color stability of the blank portion is obtained. This is considered to be one of the reasons that the present compound has a urethane structure in the molecule.
Usually, urethane exists in a keto type (-NHC (= O) O-), but when printing, very large heat energy is applied for a short time by a thermal head or the like. At that time, a change to an enol type (-N = C (-OH) O-) occurs, and it is presumed that the color developing ability is exhibited here for the first time. On the other hand, the temperature at which the stability of the heat-resistant ground color is required is about 90 to 120 ° C., and at this temperature, the conversion to the enol type does not occur and the developing ability is not exhibited. It can be said that only the phenol structure present at the end of the urethane compound causes the heat resistant ground color to deteriorate. Since the urethane compound used in the present invention has a smaller amount of the phenol moiety as compared with a generally used phenol-based developer in terms of molar ratio, it is considered that the heat-resistant ground color stability may be improved. .

Mixtures of urethane compounds having various molecular weights are formed depending on the molar ratio of the diphenol compound and the diisocyanate compound which are the raw materials for synthesis. However, since the composition of the obtained urethane compound affects the color development characteristics and image storability, It is necessary to consider these balances according to the desired performance required for the thermal recording medium. Usually, the molar ratio of the diphenol compound to the diisocyanate compound is 1.01 to
10.0 to 1.0 is appropriate, and 1.01 to 5.0 to 1.0 is more preferable. In particular, when high image storability is required, 1.0 to 3.0 to 1.0 is suitable.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The urethane compounds used in the present invention have different molecular weights by reacting a diphenol compound and a diisocyanate compound, which are raw materials for synthesis, by charging them so that the former has an excess mole number as compared with the latter. It is characterized in that a mixture of a plurality of urethane compounds is obtained. Specifically, the compound can be synthesized by dissolving an excess diphenol compound in a solvent such as acetone, methyl ethyl ketone, or pyridine, adding a diisocyanate compound thereto, and stirring the mixture at room temperature for several hours. Thereafter, the solvent in the reaction solution is distilled off, and the obtained solid is dried to obtain a target urethane compound mixture. If the diphenol compound and the diisocyanate compound are mixed, the reaction proceeds easily, and there is no need to isolate the product, so that the post-treatment operation is simple.

In addition, the diisocyanate compounds used as raw materials include diphenylmethane-4,4'-diisocyanate (trade name: MDI), tolylene-2,4-diisocyanate <2,4-TDI>, and tolylene-2,6-diisocyanate. <2,6-TDI>, 1,6-hexamethylene diisocyanate <HDI>, 1,5-naphthylene diisocyanate <NDI>, isophorone diisocyanate <IPDI>, dicyclohexylmethane-4,4 ′
-Diisocyanate <HMDI> and the like, which are industrially produced in large quantities as a raw material for coatings, adhesives, and polyurethanes, and thus can be obtained very easily and inexpensively.

The other raw material, a diphenol compound, includes bis (4-hydroxyphenyl) sulfone <B
PS>, 2-hydroxyphenyl-4'-hydroxyphenylsulfone <2,4'-BPS>, bis (2-hydroxyphenyl) sulfone <2,2'-BPS>, bis (3-hydroxyphenyl) sulfone <3 , 3'-BP
S>, 2,2-bis (4-hydroxyphenyl) propane <BPA>, catechol, resorcinol, hydroquinone, and the like, and are commercially available at relatively low cost. Also, the production can be performed at a high yield without requiring any special equipment. Therefore, when the compound of the present invention is produced using these as raw materials, there is an advantage that the cost is very low.

It should be noted that the composition of the obtained urethane compound is affected by the solvent used in the synthesis. It is presumed that the change is caused by the difference in the reaction rate depending on the solvent and the solubility in the generated urethane compound.

Specific examples of the urethane compound used in the present invention include the following combinations of raw materials, but the present invention is not limited thereto. These urethane compounds may be used alone or in combination of two or more. MEK in the table means methyl ethyl ketone, T
HF represents tetrahydrofuran, DMSO represents dimethyl sulfoxide, and DMF represents N, N-dimethylformamide.

[0028]

[Table 1] Table 1

[0029]

[Table 2] Table 2

[0030]

[Table 3] Table 3

[0031]

[Table 4] Table 4

[0032]

[Table 5] Table 5

[0033]

[Table 6] Table 6

[0034]

[Table 7] Table 7

To produce the thermosensitive recording medium of the present invention, various conventionally known production methods can be used. Specifically, it can be produced by the following method. That is,
The urethane compound, the dye precursor, the color developer, and the sensitizer of the present invention are each atomized by a pulverizer or an emulsifier such as a ball mill, an attritor, and a sand grinder, and various fillers and various additives are added. A heat-sensitive recording material can be obtained by dispersing a coating material in an aqueous solution to form a coating material and applying the coating material to an arbitrary support using an air knife coater, blade coater, roll coater, or other various coaters.

As the dye precursor used in the thermal recording medium of the present invention, conventionally known dye precursors can be used. The dye precursor is illustrated below, but is not limited thereto. These dye precursors may be used alone or in combination of two or more.

3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide <trade name: CVL
>, 3-diethylamino-6-methyl-7-anilinofluoran <ODB>, 3-dibutylamino-6-methyl-7-anilinofluoran <ODB-2>, 3- (N-
Isoamyl-N-ethylamino) -6-methyl-7-anilinofluoran <S-205>, 3-diethylamino-7-m-trifluoromethylanilinofluoran <B
rack-100>, 3-dibutylamino-7-o-chloroanilinofluoran <TH-107>, 3- (N-
Cyclohexyl-N-methylamino) -6-methyl-7
-Anilinofluoran <PSD-150>, 3-diethylamino-7-anilinofluoran <Green-2
>, 3,3-bis (4-dimethylaminophenyl) phthalide <MGL>, tris [4- (dimethylamino) phenyl] methane <LCV>, 3,3-bis (1-ethyl-
2-methylindol-3-yl) phthalide <indolyl red>, 3-cyclohexylamino-6-chlorofluoran <OR-55>, 3,3-bis [2- (p-dimethylaminophenyl) -2- (P-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide <NIR-Black>, 1,1,5,5-tetrakis (p-dimethylaminophenyl) -3-methoxy-
1,4-pentadiene, 1,1,5,5-tetrakis (p-dimethylaminophenyl) -3- (p-dimethylaminophenyl) -1,4-pentadiene.

In the present invention, the compound of the present invention can be used in combination with one or more known developers which have been conventionally used. The following are examples of color developers, but the present invention is not limited to these.

2,2-bis (4-hydroxyphenyl)
Propane, 1,7-di (4-hydroxyphenylthio)
Bisphenols such as -3,5-dioxaheptane and 4,4'-cyclohexylidenediphenol, benzyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, normal propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid 4-hydroxybenzoic acid esters such as isopropyl and butyl 4-hydroxybenzoate;
-4-hydroxyphthalic acid diesters such as dimethyl hydroxyphthalate, diisopropyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate, dihexyl 4-hydroxyphthalate, monobenzyl phthalate, monocyclohexyl phthalate, and phthalic acid Monoesters of phthalic acid such as monophenylester and monomethylphenylphthalate, bis (4-hydroxy-3-tert-butyl-6-methylphenyl) sulfide, bis (4-hydroxy-2,5-dimethylphenyl) sulfide , Bis (4-hydroxy-2
Bishydroxyphenyl sulfides such as -methyl-5-ethylphenyl) sulfide;
4-hydroxyphenylarylsulfones such as 4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-normalpropoxydiphenylsulfone, 4-hydroxyphenylbenzenesulfonate, 4- 4- such as hydroxyphenyl-p-tolylsulfonate and 4-hydroxyphenyl-p-chlorobenzenesulfonate
Hydroxyphenylarylsulfonates, 1,3-
Di [2- (4-hydroxyphenyl) -2-propyl]
1,3 such as benzene and 1,3-di [2- (4-hydroxy-3-methylphenyl) -2-propyl] benzene
-Di [2- (hydroxyphenyl) -2-propyl] benzenes, benzyl 4-hydroxybenzoyloxybenzoate, methyl 4-hydroxybenzoyloxybenzoate, ethyl 4-hydroxybenzoyloxybenzoate,
4-hydroxybenzoyloxybenzoic acid esters such as normal propyl 4-hydroxybenzoyloxybenzoate, isopropyl 4-hydroxybenzoyloxybenzoate, and butyl 4-hydroxybenzoyloxybenzoate; bis (3-tert-butyl-4-hydroxy -6-methylphenyl) sulfone, bis (3-ethyl-
4-hydroxyphenyl) sulfone, bis (3-propyl-4-hydroxyphenyl) sulfone, bis (3-isopropyl-4-hydroxyphenyl) sulfone, bis (3-ethyl-4-hydroxyphenyl) sulfone, bis (4- Bishydroxyphenyl sulfones such as (hydroxyphenyl) sulfone, 2-hydroxyphenyl-4′-hydroxyphenyl sulfone, bis (3-chloro-4-hydroxyphenyl) sulfone, and bis (3-bromo-4-hydroxyphenyl) sulfone; p-tert
Phenols such as -butylphenol, p-phenylphenol, p-benzylphenol, 1-naphthol and 2-naphthol, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, 3-sec-butyl-4
Of aromatic carboxylic acids such as -hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, terephthalic acid, salicylic acid, 3-isopropylsalicylic acid, and 3-tert-butylsalicylic acid; Metal salts.

In a thermosensitive recording medium containing a dye precursor and a color developer as a color-forming component, a sensitizer is usually used in order to increase the color-forming sensitivity. Examples of the sensitizer are shown below, but the invention is not limited thereto. These sensitizers may be used alone or in combination of two or more.

Stearic acid, stearic acid amide, palmitic acid amide, oleic acid amide, behenic acid, ethylene bisstearamide, coco fatty acid amide, montan wax, polyethylene wax, phenyl-α-naphthyl carbonate, di-p-tolyl Carbonate, diphenyl carbonate, 4-biphenyl-p-tolyl ether, p-benzylbiphenyl, m-terphenyl, triphenylmethane, 1,1,3-tris (2-methyl-
4-hydroxy-5-tert-butylphenyl) butane, 1,2-bis (3-methylphenoxy) ethane,
1,2-bisphenoxyethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-bisphenoxybutane, 1,4-bisphenoxybutene, 2-naphthylbenzyl ether, 1,4-di Ethoxynaphthalene, 1,4
-Dimethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester, 2-naphthoic acid phenyl ester,
benzyl p-benzyloxybenzoate, dibenzyl terephthalate, dimethyl terephthalate, 1,1-diphenylethanol, 1,1-diphenyl-2-propanol,
1,3-diphenoxy-2-propanol, p- (benzyloxy) benzyl alcohol, normal octadecylcarbamoyl-p-methoxycarbonylbenzene, normal octadecylcarbamoylbenzene.

In the present invention, various stabilizers may be added in order to further improve the stability of the recorded image. Examples of the stabilizer are shown below, but the invention is not limited thereto.

Zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, zinc behenate, metal salts of p-chlorobenzoate (Zn, C
a), p-nitrobenzoic acid metal salt (Zn, Ca), phthalic acid monobenzyl ester metal salt (Zn, Ca), 4,
4'-isopropylidene-bis (3-methyl-6-te
rt-butyl) phenol.

As the binder used in the heat-sensitive recording medium of the present invention, those conventionally known in the field of heat-sensitive recording can be used. Examples of the binder are described below, but the binder is not limited thereto.

Completely saponified polyvinyl alcohol having a degree of polymerization of 2000 or less, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxy Ethyl cellulose, methyl cellulose,
Cellulose derivatives such as carboxymethylcellulose and acetylcellulose, casein, gelatin, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, styrene, vinyl acetate, acrylic acid, acrylamide, acrylic acid ester and other polymers and copolymers Coalescence, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, coumarone resin, and others can be mentioned. These natural and synthetic polymer substances can be used by dissolving them in water or an organic solvent such as alcohol, or can be used in a state of being emulsified or dispersed in a paste form in a medium such as water. Also, two or more of these can be used.

The filler used in the thermal recording medium of the present invention includes clay, calcined clay, diatomaceous earth, talc, kaolin, calcium carbonate, basic magnesium carbonate, barium sulfate, barium carbonate, aluminum hydroxide, zinc oxide, silica , Magnesium hydroxide, titanium oxide, urea formalin resin, polystyrene resin, phenolic resin, and other natural or synthetic inorganic or organic fillers, but are not limited thereto. Two or more of these can be used.

As additives, ultraviolet absorbers, defoamers,
Examples include a fluorescent whitening agent, a waterproofing agent, a lubricant, and the like, but are not limited thereto.

The amounts of the dye precursor and the developer used in the thermosensitive recording medium of the present invention and the types and amounts of other various main components are as follows.
Although it is determined according to the required performance and recording suitability and is not particularly limited, usually, 1 to 8 parts of a developer and 1 to 20 parts of a filler are preferable with respect to 1 part of a dye precursor, and a binder is all solids. 10 to 25% per minute is preferred.

As the support used in the heat-sensitive recording medium of the present invention, paper such as high-quality paper, medium-quality paper, recycled paper, coated paper, and the like,
Synthetic paper, plastic film and the like can be mentioned, but the present invention is not limited to these.

For the purpose of further improving the storage stability, an overcoat layer of a polymer substance or the like can be provided on the thermosensitive coloring layer. Further, for the purpose of enhancing the storage stability and sensitivity, an undercoat layer containing an organic filler or an inorganic filler may be provided between the color-forming layer and the support.

[0051]

The present invention will be specifically described below by way of examples of synthetic examples of urethane compounds used in the present invention and production examples of thermosensitive recording materials. -Synthesis of urethane compound- [Synthesis Example 1] Synthesis of urethane compound (A-01) by reaction in MEK with BPS / MDI = 2/1 18.0 g (72 mmol) of BPS was dissolved in 80 ml of MEK. Here, under nitrogen atmosphere, 9.0 g of MDI (3
6 mmol) in 40 ml of MEK was added dropwise. The reaction was started by stirring at room temperature as it was. After 1 hour, a white precipitate had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 25.9 g of a white solid (A-01) (96% yield).
Obtained. <Melting point> 180-191 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3332,1749,1708,1587,1533,1488,143
7,1412,1362,1292,1199,1146,1103,1070,998,835,818,7
19,689,587,551 (A-01) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered off with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble content was 31.2 mg (52%), and the soluble content was 28.8 mg.
(48%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 48.9% (retention time 4.4 min), 3
4.0% (7.4 min), 5.0% (12.4 mi)
n), 2.8% (28.8 min)

[Synthesis Example 2] BPS / MDI = 1.5 /
Urethane compound (A-0)
2) Synthesis 6.0 g (24 mmol) of BPS was dissolved in 20 ml of MEK. Here, under nitrogen atmosphere, 4.0 g of MDI (16
(mmol) in 10 ml of MEK was added dropwise. The reaction was started by stirring at room temperature as it was. After 1 hour, a white precipitate had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 9.6 g (96% yield) of a white solid (A-02). <Melting point> 178-187 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3340,1763,1725,1589,1536,1488,141
2,1315,1293,1200,1146,1105,999,836,817,716,691,59
0,552 (A-02) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble matter was 39.6 mg (66%), and the soluble matter was 20.4 mg.
(34%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 65.4% (retention time 4.4 min), 1
8.7% (7.4 min), 8.4% (12.4 mi)
n), 1.2% (28.8 min)

[Synthesis Example 3] BPS / MDI = 1.2 /
Urethane compound (A-0)
3) Synthesis 6.0 g (24 mmol) of BPS was dissolved in 20 ml of MEK. Here, 5.0 g of MDI (20
(mmol) in 20 ml of MEK was added dropwise. The reaction was started by stirring at room temperature as it was. After 45 minutes, a white precipitate had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 10.5 g (yield 95%) of a white solid (A-03).
Obtained. <Melting point> 189-193 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3342,1761,1728,1590,1534,1488,141
1,1316,1294,1199,1148,1105,999,838,817,711,591,553 (A-03) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble content was 54.7 mg (91%), and the soluble content was 5.3 mg (9%).
%)Met. Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 82.3% (retention time 4.4 min);
2% (7.4 min), 9.7% (12.4 min)

[Synthesis Example 4] Urethane compound (A-04) by reaction in acetone at BPS / MDI = 2/1
Synthesis BPS 18.0 g (72 mmol) in acetone 80 ml
Was dissolved. Here, under nitrogen atmosphere, MDI 9.0g
A solution of (36 mmol) in 40 ml of acetone was added dropwise. The reaction was started by stirring at room temperature as it was.
After 1 hour, a white precipitate had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 26.4 g (yield 98%) of a white solid (A-04). <Melting point> 120-170 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3336,1748,1728,1708,1587,1534,148
8,1438,1412,1363,1292,1200,1147,1105,1070,999,836,
818,719,691,590,553 (A-04) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble matter was 32.2 mg (54%), and the soluble matter was 27.8 mg.
(46%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 46.8% (retention time 4.4 min), 3
5.1% (7.4 min), 4.8% (12.4 mi)
n), 2.9% (28.8 min)

Synthesis Example 5 Synthesis of Urethane Compound (A-05) by Reaction in THF at BPS / MDI = 2/1 6.0 g (24 mmol) of BPS was dissolved in 20 ml of THF. Here, 3.0 g of MDI (12
(mmol) in 10 ml of THF was added dropwise. The reaction was started by stirring at room temperature as it was. After 1 hour, a white precipitate had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 8.8 g (yield 98%) of a white solid (A-05). <Melting point> 135-142 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3335,1749,1587,1534,1488,1439,141
3,1292,1199,1147,1105,1070,999,836,719,691,590,553 (A-05) 60.0 mg in 100 ml of acetonitrile
Was added, and the mixture was stirred at room temperature for 30 minutes, filtered with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble matter was 28.2 mg (47%), and the soluble matter was 31.8 mg.
(53%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 36.1% (retention time 4.4 min), 3
9.9% (7.4 min), 15.0% (12.4 mi)
n), 2.2% (28.8 min)

[Synthesis Example 6] Urethane compound (A-06) obtained by reaction in pyridine with BPS / MDI = 2/1
Synthesis BPS (6.0 g, 24 mmol) was dissolved in pyridine (20 ml). Here, 3.0 g of MDI (1
A solution of 2 mmol) in 10 ml of pyridine was added dropwise. The reaction was started by stirring at room temperature as it was. A white precipitate did not precipitate and remained a clear solution. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain a white solid (A-06) at 8.5.
g (94% yield). <Melting point> 180-220 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3367,3315,1750,1723,1586,1536,148
9,1440,1411,1289,1200,1142,1103,1068,1003,835,691,
645,587,552 (A-06) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble content was 16.0 mg (27%), and the soluble content was 44.0 mg.
(73%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 64.1% (retention time 4.4 min), 1
0.4% (7.4 min), 4.4% (12.4 mi)
n) 1.3% (28.8 min)

[Synthesis Example 7] Urethane compound (A-07) obtained by a reaction in DMSO with BPS / MDI = 2/1
Synthesis BPS (6.0 g, 24 mmol) was dissolved in DMSO (20 ml). Here, 3.0 g of MDI (1
2 mmol) in 10 ml of DMSO was added dropwise. The reaction was started by stirring at room temperature as it was. A white precipitate did not precipitate and remained a clear solution. The reaction was performed for a total of 3 hours. After completion of the reaction, the reaction solution was poured into 500 ml of water, and the resulting solid was collected by filtration and dried to give a white solid (A-0).
6.8 g (yield 76%) of 7) was obtained. <Melting point> 135-155 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3368,1750,1600,1532,1489,1438,141
2,1290,1200,1147,1105,1002,837,721,692,588,555 (A-07) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered off with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble content was 20.1 mg (34%), and the soluble content was 39.9 mg.
(66%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 58.2% (retention time 4.4 min), 1
8.7% (7.4 min), 8.1% (12.4 mi)
n), 4.7% (28.8 min)

Synthesis Example 8 Synthesis of Urethane Compound (A-08) by Reaction in DMF with BPS / MDI = 2/1 6.0 g (24 mmol) of BPS was dissolved in 20 ml of DMF. Here, 3.0 g of MDI (12
(mmol) in 10 ml of DMF was added dropwise. The reaction was started by stirring at room temperature as it was. A white precipitate did not precipitate and remained a clear solution. The reaction was performed for a total of 3 hours. After completion of the reaction, the reaction solution was poured into 500 ml of water, and the resulting solid was collected by filtration and dried to give a white solid (A-0).
7.9 g (yield 88%) of 8) was obtained. <Melting point> 110-128 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3332,1752,1655,1586,1535,1488,143
7,1412,1386,1290,1197,1147,1103,994,836,690,587,55
3 (A-08) 60.0 mg in 100 ml of acetonitrile
Was added, and the mixture was stirred at room temperature for 30 minutes, separated by filtration through a membrane filter, and the filter cake and the filtrate were dried and weighed.
(53%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 50.9% (retention time 4.4 min);
0% (7.4 min), 5.3% (12.4 min),
1.0% (28.8 min)

Synthesis Example 9 BPS / MDI = 2.5 /
Urethane compound (A-0)
9) Synthesis 42.5 g (170 mmol) of BPS was added to acetone 190
Dissolved in ml. Here, MDI 17.
A solution of 0 g (68 mmol) in 80 ml of acetone was added dropwise. The reaction was started by stirring at room temperature as it was. After 1 hour, a white precipitate had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 56.5 g (yield: 95%) of a white solid (A-09). <Melting point> 120-178 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3366,1749,1726,1709,1587,1536,148
8,1439,1413,1363,1292,1201,1144,1104,1071,999,836,
818,721,691,588,552 (A-09) 60.0 mg in 100 ml of acetonitrile
Was added, and the mixture was stirred at room temperature for 30 minutes, filtered off with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble content was 17.4 mg (29%) and the soluble content was 42.6 mg.
(71%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 65.1% (retention time 4.4 min);
0% (7.4 min), 3.1% (12.4 min),
1.0% (28.8 min)

[Synthesis Example 10] BPS / MDI = 3/1
Urethane compound (A-1)
0) Synthesis BPS 45.0 g (180 mmol) was added to acetone 200
Dissolved in ml. Here, MDI15.
A solution of 0 g (60 mmol) in 70 ml of acetone was added dropwise. The reaction was started by stirring at room temperature as it was. After 1 hour, a white precipitate had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 57.8 g (yield: 96%) of a white solid (A-10). <Melting point> 120-185 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3409,3370,1749,1726,1587,1536,148
9,1439,1413,1363,1291,1224,1201,1144,1104,1071,100
0,836,818,722,691,588,552 (A-10) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered off with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble matter was 9.6 mg (16%) and the soluble matter was 50.4 mg (8%).
4%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column is ODS (manufactured by GL Science), mobile phase is acetonitrile / water / phosphoric acid = 70/3)
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 70.2% (retention time 4.4 min);
0% (7.4 min), 1.4% (12.4 min),
1.5% (28.8 min)

[Synthesis Example 11] BPS / 2,4-TDI
= 2/1 urethane compound (A) by reaction in MEK
-11) Synthesis 8.0 g (32 mmol) of BPS was dissolved in 30 ml of MEK. Here, under a nitrogen atmosphere, 2,4-TDI2.7
A solution of 8 g (16 mmol) dissolved in 10 ml of MEK was added dropwise. The reaction was started by stirring at room temperature as it was. After 1 hour, a white solid had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 10.0 g (yield 93%) of a white solid (A-11). <Melting point> 170-240 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3409,3370,1760,1721,1587,1535,148
8,1443,1407,1292,1203,1145,1104,1071,1018,1013,83
7,722,692,586,550 (A-11) 60.0 mg in 100 ml of acetonitrile
Was added, and the mixture was stirred at room temperature for 30 minutes, filtered with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble matter was 32.7 mg (55%), and the soluble matter was 27.3 mg.
(45%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 73.0% (retention time 4.4 min), 1
6.5% (8.7 min)

[Synthesis Example 12] BPS / HDI = 2/1
Urethane Compound (A-25) by Reaction in MEK
Synthesis BPS 8.0 g (32 mmol) was dissolved in MEK 30 ml. Here, 2.69 g of HDI (1
(6 mmol) in 10 ml of MEK was added dropwise. The reaction was started by stirring at room temperature as it was. After 1 hour, a white solid had formed. The reaction was performed for a total of 3 hours. After completion of the reaction, the solvent was distilled off using an evaporator, and the solid was dried under reduced pressure to obtain 10.1 g of a white solid (A-25) (yield 94%).
Obtained. <Melting point> 149-155 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3345,2940,2856,1712,1587,1531,148
8,1440,1405,1291,1212,1150,1104,1069,1013,982,836,
720,693,607,584,552 (A-25) 60.0 mg in 100 ml of acetonitrile
And the mixture was stirred at room temperature for 30 minutes, filtered with a membrane filter, and the filter cake and the filtrate were dried and weighed. The insoluble content was 30.6 mg (51%), and the soluble content was 29.4 mg.
(49%). Further, HPLC analysis was performed on soluble components. <HPLC analysis> (column: ODS (GL Science), mobile phase: acetonitrile / water / phosphoric acid = 70/3
0 / 0.5, detection wavelength 254 nm, flow rate 1 ml / mi
n) peak area 41.9% (retention time 4.4 min), 3
6.1% (5.4 min), 16.2% (5.9 mi)
n) 1.6% (9.3 min), 2.2% (9.9 m)
in), 0.3% (12.7 min), 0.2% (1
4.1 min)

-Production of thermosensitive recording medium- [Examples 1 to 12] Thermosensitive recording media comprising the following compositions were produced. That is, first, a dye dispersion (solution A) and a developer dispersion (solution B) having the following composition were each ground by a sand grinder to an average particle diameter of 1 μm. (Solution A: dye dispersion) 3-N, N-diethylamino-6-methyl-7-anilinofluoran 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts (Solution B: color development Agent Dispersion) Developer (see Table 1) 6.0 parts 10% aqueous solution of polyvinyl alcohol 18.8 parts Water 11.2 parts Then, dispersions of A liquid, B liquid and kaolin clay are mixed at the following ratios. This was used as a heat-sensitive coating. Solution A: Dye dispersion 9.2 parts Solution B: developer dispersion 36.0 parts Kaolin clay (50% dispersion) 12.0 parts Amount of this heat-sensitive paint applied to one side of a 50 g / m ² base paper 6.
The sheet was coated and dried so as to have a thickness of 0 to 6.5 g / m ² , and this sheet was treated with a super calender so that the smoothness became 500 to 600 seconds, thereby producing a thermosensitive recording medium.

[Comparative Examples 1 to 4] Heat-sensitivity was performed in the same manner as in Examples 1 to 12 except that the following developer was used in place of the compound of the present invention in the developer dispersion (solution B). A recording medium was produced. 2,2-bis (4-hydroxyphenyl) propane (B
-01) Bis (4-hydroxyphenyl) sulfone (B-02) Urethane compound (B-03) synthesized by reaction in MEK with BPS / MDI = 20/1 MEK with BPS / MDI = 1 / 1.5 Compound (B-04) synthesized by the reaction in

-Evaluation of thermal recording medium- [Coloring method]
01 (made by UBI) with an applied energy of 0.41
Recording was performed on the produced thermosensitive recording medium at mj / dot.
Next, the image density of the recording portion and the blank portion was measured by a Macbeth densitometer (RD-914, using an amber filter). Using this as a test sample, the following test was performed. [Plasticizer resistance test]: The test sample was brought into contact with a vinyl chloride film (Dialup 300G, manufactured by Mitsubishi Plastics, Inc.), left at 40 ° C. for 24 hours, and the image remaining density of the recording portion was measured with a Macbeth densitometer. . [Oil resistance test]: The test sample was immersed in salad oil for 1 hour, the oil was wiped off, left at room temperature for 24 hours, and the residual image density of the recording portion was measured with a Macbeth densitometer. [Water resistance test]: The test sample was immersed in tap water for 24 hours, dried at 30 ° C. for 2 hours, and the image remaining density of the recording portion was measured with a Macbeth densitometer. [Heat-resistant ground color test of blank portion]: The test sample was left at 100 ° C. for 30 minutes, and the density of the blank portion was measured with a Macbeth densitometer.

Table 8 shows the results of the image storability test of the image recording section.
Table 9 shows the results of the heat-resistant ground color test on the blank portion. In Table 8, the larger the value, the better the image storability, and in Table 9, the smaller the value, the better the stability of the heat-resistant ground color.

[0067]

[Table 8] Table 8. Image storage test results

[0068]

[Table 9] Table 9. Results of heat resistant ground color test

As is clear from the results of Tables 8 and 9, Examples 1 to 12 using the compounds of the present invention as developers were
Compared with Comparative Examples 1 and 2 using a conventional phenolic developer, the image storage property of the recording portion is remarkably improved, and the heat resistant ground color stability of the blank portion is also excellent. Further, Comparative Example 3 using a urethane compound obtained by reacting a diphenol compound and a diisocyanate compound at a molar ratio of 20: 1, and Comparative Example 4 using a urethane compound synthesized by increasing the diisocyanate compound from the diphenol compound in excess. It is clearly superior in comparison.

[0070]

The compounds of the present invention have sufficient ability to form a dye precursor. Further, a heat-sensitive recording material using this compound as a color developer is extremely useful because it is very excellent in image storability of a recording portion and heat-resistant ground color stability of a blank portion.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichi Yanagiuchi 5-2-1-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Central Research Laboratory (72) Inventor Seiki Yoneshi 5-21, Oji, Kita-ku, Tokyo No. 1 Nippon Paper Industries Central Research Laboratory (72) Inventor Hidetoshi Yoshioka 2-1-1, Iida-cho, Iwakuni-shi, Yamaguchi Prefecture Nippon Paper Industries Co., Ltd. Chemical Product Research Laboratory F-term (reference) 2H026 AA07 BB28 DD12

Claims (5)

[Claims] 1. A thermosensitive recording medium having a thermosensitive coloring layer containing a colorless or pale-colored dye precursor and a developer that reacts upon heating to form the dye precursor, wherein the developer is diphenol. A thermosensitive recording material, which is a urethane compound obtained by reacting a compound with a diisocyanate compound at a molar ratio of 1.01 to 10.0 to 1.0. 2. A diphenol compound represented by the following general formula (1):
The heat-sensitive recording material according to claim 1, wherein the diisocyanate compound is a compound represented by the following general formula (2). Embedded image (However, R ¹ and R ² each represent an alkyl group, an alkoxy group, or an electron-withdrawing group. L and m each represent an integer of 0 to 4. n and o each represent an integer of 1 to 5. A Represents a divalent group.) 3. The thermosensitive recording medium according to claim 2, wherein the diisocyanate compound represented by the general formula (2) is a compound represented by the following formula (3). Embedded image 4. The thermosensitive recording medium according to claim 2, wherein the diisocyanate compound represented by the general formula (2) is a compound represented by the following formula (4). Embedded image 5. The thermosensitive recording material according to claim 2, wherein the diisocyanate compound represented by the general formula (2) is a compound represented by the following formula (5). Embedded image (P represents an integer of 2 to 12.)